I thoroughly failed to process that when I read the comics, but Lowe doesn't understand familial relations. Raze is the future son of Logan and Raven, giving Kurt a younger half-brother. With a little bit of stretching, assuming Logan and Raven never marry, Logan could be considered Kurt's step-father. If they do get married, Logan would legally be Kurt's step-father for that period. Now, that would be funny. Don't ask me how Lowe got to uncle.